Customer response to the 2006 Dodge Ram 1500 will be watched closely
in the next few months as fullsize trucks come off a most impressive summer
sales spree. Industry observers have to ask: Who’s left to buy a
big truck? And if anyone is shopping this fall, will prices at the gas
pump scare them away?

To complement
news about the new Mega Cab model, the 2006 Ram 1500 has been given a
midlife exterior facelift, interior freshening and upgraded frame and
suspension. The changes should attract consumer attention as the fullsize
offerings from Chevy, GMC and Toyota are finishing up their last year
before redesigned models are introduced. Nissan Titan sales continue to
eek upward with no major changes expected, but the truck is still wanting
for a solid foothold in America’s breadbasket. The Ford F-150 should
cruise along with only a few minor cosmetic changes this year.

Perhaps the
most anticipated feature of the new Ram 1500 is the multi-displacement
system (MDS) added to the Hemi engine. Dodge officials promise this new
technology can improve fuel economy with no loss of power. With gas prices
hovering near the $3-per-gallon mark in many areas now, even the most
hard-crusted pickup enthusiast will be looking to lower his monthly running
costs.

MDS allows the Hemi to transition from eight cylinders to four in just
40 milliseconds, which is quicker than the blink of an eye. The switch
takes place when there’s little or no load on the engine, such as
cruising the Interstate where engineers say it only takes about 20 or
30 horsepower to keep a vehicle moving. Long hauls on open roads with
a steady speed should result in the most noticeable savings. Despite the
promise that “customers will experience fuel economy gains of up
to 20 percent under certain driving conditions,” Dodge didn’t
change the EPA estimated fuel economy ratings for the 2006 Hemi-power
Ram 1500 pickup. The 2005 and 2006 press materials state the EPA numbers
as 14 city/18 highway for the 2-wheel-drive models and 13/17 for the 4WD
trucks.

The MDS operation
is very smooth. Unlike the Honda Odyssey minivan, which has a similar
system that cuts out three of the engine’s six cylinders while cruising,
there is no indicator on the dash to let the driver know how many of the
Hemi’s cylinders are firing. Trying to determine when MDS kicks
in or out is futile, even with the quieter noise levels in the cab. Stabbing
the throttle off cruising speed offers normal acceleration and transmission
kickdown.

The on-board engine-management computer controls the MDS. The four cylinders
that can be deactivated are numbers 1,4,6 and 7. That includes the two
inner cylinders on one back and the two outer cylinders on the opposing
bank. By shutting down these specific cylinders at once, the engine can
maintain regular 180-degree firings as a V4. Hemi engineers designed the
cylinder block with a specific oil circuit to support MDS. Four solenoids
control oil pressure to eight specially designed hydraulic-roller lifters
that control the intake and exhaust valves in the cylinders to be deactivated.
When the solenoids are activated, high-pressure oil is fed to the lifters.
A pin in each lifter is moved, disconnecting the outer portion of the
lifter from the inner. The outer portion of the lifter continues to ride
along the camshaft lobes but the inner portion, which supports the pushrod,
remains still. With both valves closed, the engine computer also shuts
off the spark and fuel to those cylinders.